The Obama administration is reportedly considering airstrikes in Syria against the terrorist group ISIS. The New York Times quotes "a top national security adviser" to the president as saying the U.S. is "'not going to be restricted by borders' to protect its interests..."

What about American cities? If ISIS attacks one or more U.S. cities, as it has threatened to do, what then? We can't bomb ourselves. How would we counter a nosedive in the stock market or the ensuing chaos and fear?

The U.S. and Europe are vulnerable because of a false belief that we can somehow "convert" ideological and religious fundamentalists into pluralistic, tolerant people by exposing them to our way of life. So we let them into our nations. They build mosques, often with funding from Saudi Arabia, which practices and teaches a radical brand of Islam known as Wahhabism, and allow them to set up Islamic schools, at least some of which teach hatred of Jews, Christians and Western values.

France has seen its Muslim population explode to more than 8 million, and growing, according to the Gatestone Institute. It is the same in other European nations. While not all of these immigrants are terrorists, no doubt terrorists immigrated along with those looking for a better life, or were radicalized after arriving. Many Muslim immigrants have lived in isolation from Western cultures and values which their faith has taught them to hate.

According to the Pew Research Religion & Public Life Project, "the estimated share of legal Muslim immigrants entering the U.S. each year has roughly doubled, from about 5 percent of legal immigrants in 1992 to about 10 percent in 2012." While it is a diverse group with not all holding to the same ideology or hatred of the West, there are enough radicals among them to constitute a clear and present danger. Groups like the Council on American–Islamic Relations (CAIR) intimidate some politicians and the media with cries of "Islamophobia" whenever anyone warns of the radicals' agenda.

As the Center for Immigration Studies points out, "Since the November 1990 assassination of Rabbi Meir Kahane by an Egyptian, the immigrant Muslim community has been associated with a great number of violent incidents -- all these even before the atrocities on September 11, 2001. In its long history of immigration, the United States has never encountered so violent-prone and radicalized a community as the Muslims who have arrived since 1965."

So, if even a small number of Muslim immigrants -- or American citizens who have been radicalized by imams -- attack a shopping mall, killing and terrorizing shoppers, what will the president do? Will he treat it as a crime, "workplace violence," or call it by its right name? Will civil libertarians have their way in opposing further surveillance of potential and actual radicals, deporting some and stripping others of their U.S. citizenship, if they travel to align themselves with ISIS fighters and try to return to the U.S.? Will they be allowed in? They should be barred.

These and many other questions must be answered before another attack, which our leaders repeatedly warn is coming. Why is it coming? Because presidents over several administrations have not done all they could to prevent it, preferring soft words to tough action. What will the current president do when the next attack comes? Will the public take matters into their own hands and fight back?

Vigilantes are the last thing we need, but they could rise up, if government fails to perform its constitutional duty to protect us from enemies, foreign and domestic.